381 research outputs found
On the relation between the mass of Compact Massive Objects and their host galaxies
Supermassive black holes and/or very dense stellar clusters are found in the
central regions of galaxies. Nuclear star clusters are present mainly in faint
galaxies while upermassive black holes are common in galaxies with masses M. In the intermediate galactic mass range both types of
central massive objects (CMOs) are found. Here we present our collection of a
huge set of nuclear star cluster and massive black hole data that enlarges
significantly already existing data bases useful to investigate for
correlations of their absolute magnitudes, velocity dispersions and masses with
structural parameters of their host galaxies. In particular, we directed our
attention to some differences between the correlations of nuclear star clusters
and massive black holes as subsets of CMOs with hosting galaxies. In this
context, the mass-velocity dispersion relation plays a relevant role because it
seems the one that shows a clearer difference between the supermassive black
holes and nuclear star clusters. The has a slope of while has the much smaller slope of .
The slopes of the CMO mass- host galaxy B magnitude of the two types of CMOs
are indistinguishable within the errors while that of the NSC mass-host galaxy
mass relation is significantly smaller than for supermassive black holes.
Another important result is the clear depauperation of the NSC population in
bright galaxy hosts, which reflects also in a clear flattening of the NSC mass
vs host galaxy mass at high host masses.Comment: 12 pages, 22 figures, 2 tables, accepted for publication in MNRA
Kinematic study of the parsec-scale jet of the quasar PKS 1741–03
We present 23 interferometric images of the parsec-scale jet of the quasar PKS 1741–03 at\ud
15, 24 and 43 GHz, spanning about 13 yr. We model the images as a superposition of discrete\ud
two-dimensional elliptical Gaussian components, with parameters determined by the crossentropy\ud
technique. All the images present a spatially unresolved component (core) and usually\ud
two or three components receding from it. The same components were found in simultaneous\ud
24- and 43-GHz maps, showing the robustness of our model fitting. The core-shift opacity\ud
effect between these frequencies is weak.We have identified seven components moving along\ud
straight lines at constant apparent superluminal speeds (3.5 βobs 6.1), with different sky\ud
position angles (−186◦ η −125◦). The core flux density tracks quite well the fluctuations\ud
seen in the historical single-dish light curve at 14.5 GHz, with no measurable delay. The total\ud
flux density from the moving jet components is delayed∼2 yr in relation to the core light curve,\ud
roughly the same as the lag between the ejection epoch and the maximum flux density in the\ud
light curves of the jet components.We propose that there are three non-exclusive mechanisms\ud
for producing these delays. From the kinematics of the most robust jet components and the\ud
core brightness temperature, we determined the bulk Lorentz factor (4.8 γ 24.5) and\ud
the jet viewing angle (0. ◦ 35 θ 4. ◦ 2); these values agree with previous estimates from the\ud
spectral energy distribution of PKS 1741–03 and its radio variabilityFAPESPCNPqCAPESINCTNational Science Foundation - AST-0607523NASA Fermi - NNX09AU16G, NMX10AP16G, NMX11AO13
Multi-band analyses of the bright GRB~230812B and the associated SN2023pel
GRB~230812B is a bright and relatively nearby () long gamma-ray
burst that has generated significant interest in the community and therefore
has been subsequently observed over the entire electromagnetic spectrum. We
report over 80 observations in X-ray, ultraviolet, optical, infrared, and
sub-millimeter bands from the GRANDMA (Global Rapid Advanced Network for
Multi-messenger Addicts) network of observatories and from observational
partners. Adding complementary data from the literature, we then derive
essential physical parameters associated with the ejecta and external
properties (i.e. the geometry and environment) and compare with other analyses
of this event (e.g. Srinivasaragavan et al. 2023). We spectroscopically confirm
the presence of an associated supernova, SN2023pel, and we derive a
photospheric expansion velocity of v 17 km . We
analyze the photometric data first using empirical fits of the flux and then
with full Bayesian Inference. We again strongly establish the presence of a
supernova in the data, with an absolute peak r-band magnitude . We find a flux-stretching factor or relative brightness and a time-stretching factor ,
both compared to SN1998bw. Therefore, GRB 230812B appears to have a clear long
GRB-supernova association, as expected in the standard collapsar model.
However, as sometimes found in the afterglow modelling of such long GRBs, our
best fit model favours a very low density environment (). We also find small values for
the jet's core angle and
viewing angle. GRB 230812B/SN2023pel is one of the best characterized
afterglows with a distinctive supernova bump
The Power Board of the KM3NeT Digital Optical Module: design, upgrade, and production
The KM3NeT Collaboration is building an underwater neutrino observatory at
the bottom of the Mediterranean Sea consisting of two neutrino telescopes, both
composed of a three-dimensional array of light detectors, known as digital
optical modules. Each digital optical module contains a set of 31 three inch
photomultiplier tubes distributed over the surface of a 0.44 m diameter
pressure-resistant glass sphere. The module includes also calibration
instruments and electronics for power, readout and data acquisition. The power
board was developed to supply power to all the elements of the digital optical
module. The design of the power board began in 2013, and several prototypes
were produced and tested. After an exhaustive validation process in various
laboratories within the KM3NeT Collaboration, a mass production batch began,
resulting in the construction of over 1200 power boards so far. These boards
were integrated in the digital optical modules that have already been produced
and deployed, 828 until October 2023. In 2017, an upgrade of the power board,
to increase reliability and efficiency, was initiated. After the validation of
a pre-production series, a production batch of 800 upgraded boards is currently
underway. This paper describes the design, architecture, upgrade, validation,
and production of the power board, including the reliability studies and tests
conducted to ensure the safe operation at the bottom of the Mediterranean Sea
throughout the observatory's lifespa
GRANDMA and HXMT Observations of GRB 221009A -- the Standard-Luminosity Afterglow of a Hyper-Luminous Gamma-Ray Burst
GRB 221009A is the brightest Gamma-Ray Burst (GRB) detected in more than 50
years of study. In this paper, we present observations in the X-ray and optical
domains after the GRB obtained by the GRANDMA Collaboration (which includes
observations from more than 30 professional and amateur telescopes) and the
Insight-HXMT Collaboration. We study the optical afterglow with empirical
fitting from GRANDMA+HXMT data, augmented with data from the literature up to
60 days. We then model numerically, using a Bayesian approach, the GRANDMA and
HXMT-LE afterglow observations, that we augment with Swift-XRT and additional
optical/NIR observations reported in the literature. We find that the GRB
afterglow, extinguished by a large dust column, is most likely behind a
combination of a large Milky-Way dust column combined with moderate
low-metallicity dust in the host galaxy. Using the GRANDMA+HXMT-LE+XRT dataset,
we find that the simplest model, where the observed afterglow is produced by
synchrotron radiation at the forward external shock during the deceleration of
a top-hat relativistic jet by a uniform medium, fits the multi-wavelength
observations only moderately well, with a tension between the observed temporal
and spectral evolution. This tension is confirmed when using the extended
dataset. We find that the consideration of a jet structure (Gaussian or
power-law), the inclusion of synchrotron self-Compton emission, or the presence
of an underlying supernova do not improve the predictions, showing that the
modelling of GRB22109A will require going beyond the most standard GRB
afterglow model. Placed in the global context of GRB optical afterglows, we
find the afterglow of GRB 221009A is luminous but not extraordinarily so,
highlighting that some aspects of this GRB do not deviate from the global known
sample despite its extreme energetics and the peculiar afterglow evolution.Comment: Accepted to ApJL for the special issue, 37 pages, 23 pages main text,
6 tables, 13 figure
Ready for O4 II: GRANDMA Observations of Swift GRBs during eight-weeks of Spring 2022
We present a campaign designed to train the GRANDMA network and its
infrastructure to follow up on transient alerts and detect their early
afterglows. In preparation for O4 II campaign, we focused on GRB alerts as they
are expected to be an electromagnetic counterpart of gravitational-wave events.
Our goal was to improve our response to the alerts and start prompt
observations as soon as possible to better prepare the GRANDMA network for the
fourth observational run of LIGO-Virgo-Kagra (which started at the end of May
2023), and future missions such as SM. To receive, manage and send out
observational plans to our partner telescopes we set up dedicated
infrastructure and a rota of follow-up adcates were organized to guarantee
round-the-clock assistance to our telescope teams. To ensure a great number of
observations, we focused on Swift GRBs whose localization errors were generally
smaller than the GRANDMA telescopes' field of view. This allowed us to bypass
the transient identification process and focus on the reaction time and
efficiency of the network. During 'Ready for O4 II', 11 Swift/INTEGRAL GRB
triggers were selected, nine fields had been observed, and three afterglows
were detected (GRB 220403B, GRB 220427A, GRB 220514A), with 17 GRANDMA
telescopes and 17 amateur astronomers from the citizen science project
Kilonova-Catcher. Here we highlight the GRB 220427A analysis where our
long-term follow-up of the host galaxy allowed us to obtain a photometric
redshift of , its lightcurve elution, fit the decay slope of the
afterglows, and study the properties of the host galaxy
Embedded Software of the KM3NeT Central Logic Board
The KM3NeT Collaboration is building and operating two deep sea neutrino
telescopes at the bottom of the Mediterranean Sea. The telescopes consist of
latices of photomultiplier tubes housed in pressure-resistant glass spheres,
called digital optical modules and arranged in vertical detection units. The
two main scientific goals are the determination of the neutrino mass ordering
and the discovery and observation of high-energy neutrino sources in the
Universe. Neutrinos are detected via the Cherenkov light, which is induced by
charged particles originated in neutrino interactions. The photomultiplier
tubes convert the Cherenkov light into electrical signals that are acquired and
timestamped by the acquisition electronics. Each optical module houses the
acquisition electronics for collecting and timestamping the photomultiplier
signals with one nanosecond accuracy. Once finished, the two telescopes will
have installed more than six thousand optical acquisition nodes, completing one
of the more complex networks in the world in terms of operation and
synchronization. The embedded software running in the acquisition nodes has
been designed to provide a framework that will operate with different hardware
versions and functionalities. The hardware will not be accessible once in
operation, which complicates the embedded software architecture. The embedded
software provides a set of tools to facilitate remote manageability of the
deployed hardware, including safe reconfiguration of the firmware. This paper
presents the architecture and the techniques, methods and implementation of the
embedded software running in the acquisition nodes of the KM3NeT neutrino
telescopes
Prospects for combined analyses of hadronic emission from -ray sources in the Milky Way with CTA and KM3NeT
The Cherenkov Telescope Array and the KM3NeT neutrino telescopes are major
upcoming facilities in the fields of -ray and neutrino astronomy,
respectively. Possible simultaneous production of rays and neutrinos
in astrophysical accelerators of cosmic-ray nuclei motivates a combination of
their data. We assess the potential of a combined analysis of CTA and KM3NeT
data to determine the contribution of hadronic emission processes in known
Galactic -ray emitters, comparing this result to the cases of two
separate analyses. In doing so, we demonstrate the capability of Gammapy, an
open-source software package for the analysis of -ray data, to also
process data from neutrino telescopes. For a selection of prototypical
-ray sources within our Galaxy, we obtain models for primary proton and
electron spectra in the hadronic and leptonic emission scenario, respectively,
by fitting published -ray spectra. Using these models and instrument
response functions for both detectors, we employ the Gammapy package to
generate pseudo data sets, where we assume 200 hours of CTA observations and 10
years of KM3NeT detector operation. We then apply a three-dimensional binned
likelihood analysis to these data sets, separately for each instrument and
jointly for both. We find that the largest benefit of the combined analysis
lies in the possibility of a consistent modelling of the -ray and
neutrino emission. Assuming a purely leptonic scenario as input, we obtain, for
the most favourable source, an average expected 68% credible interval that
constrains the contribution of hadronic processes to the observed -ray
emission to below 15%.Comment: 18 pages, 15 figures. Submitted to journa
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